Why RowExpander need grid to be locking to work?

Why RowExpander need grid to be locking to work?

When I config grid enableLocking to false, the grid is empty. In Ext.grid.plugin.RowExpander, there is a condition in setCmp function that check grid is locking enabled. I remove that condition and the RowExpander work without needing grid to be locking.

It would be wonderful if grid does not need to locking before we can use RowExpander.